I had second (third?) thoughts about doing this myself.. Like most handi people, I have chased threads a thousand times.. I have re threaded with a different thread more than a few times...mostly heli-coil and the like. This needs to be a lil more precision...

SO I enlisted the help of a good engineering friend. He took it into his shop and lathe bored the opening to remove threads and prep the bore to the correct dia hole for the 11/16x24 tap. I think he said .645. Then he tapped the hole.

As expected its perfect and 100% aligned with the hole at the end where the bullet exits! Kind'a impotent as Al pointed out couple posts back. (Thanks man!!)